Data-Over-Cable Service Interface Specifications (“DOCSIS”) has been established by cable television network operators to facilitate transporting data traffic, primarily internet traffic, over existing community antenna television (“CATV”) networks. In addition to transporting data traffic as well as television content signals over a CATV network, multiple services operators (“MSO”) also use their CATV network infrastructure for carrying voice, video on demand (“VoD”) and video conferencing traffic signals, among other types.
In transporting downstream multimedia content, as well as data, an upstream message, or messages, is/are typically sent to request the content and to set up a service flow to deliver the content. In addition to downstream multimedia content, such as video, voice traffic also uses message signaling to set up service flows for the upstream and downstream directions.
These signals are typically sent over a fiber network to a location, sometimes referred to as a node, near an end user, and from the node to a broadband user's device via a coaxial cable. Such an arrangement is known in the art as a hybrid fiber coaxial network (“HFC”). An HFC network may be designed for redundancy by configuring portions in rings. Thus, from any one point to another that is connected by a ring, there are two routes a signal can take in traveling between one point and another. This provides redundancy inasmuch as if the ring is severed at a point along a given route, signals that were traveling along that route can be rerouted from their origination point to destination point in the other direction.
As known in the art, broadband user devices, also referred to as customer premise equipment devices, such as, for example, DOCSIS cable modems, DOCSIS media terminal adaptors (“MTA”), embedded MTA (“EMTA”), or DOCSIS set top gateway devices, undergo a process commonly referred to as ranging and registering upon start-up. During this process, the distance along the route connecting a modem, or modems, to a central device, such as a cable modem termination system (“CMTS”), is determined and stored. This distance is used for timing purposes to regulate when a given device can transmit so that collisions do not occur between multiple modems using the same channel to communicate with the CMTS. Accuracy and precision in determining the correct distance between the modem and the CMTS is important to prevent interference, or collision, as referred to in the art, between traffic signals of the modems.
When a portion of a network ring is severed, the distance between the modem and the CMTS changes when a ring protection switch occurs. A ring protection switch re-routes traffic that was using the now-severed portion so that the same traffic flows over an intact portion. However, the distance, and thus signal delay, between modems subject to the ring protection switch and the CMTS, is altered. Thus, even though there is a back-up path for modems to use instead of the route having the severed portion, the distance for such modems will almost assuredly be changed. This affects a change in the time for a signal to reach the CMTS, and the modems that were connected to the CMTS via the severed link typically undergo the range and register process again, which induces a perceptible service interruption for the users of these modems while the modems are restarting/rebooting. Furthermore, when one or more modems continue to transmit under the assumption that the old range delay is still in effect, the ability of other modems to properly re-range and re-register is negatively impacted.
Thus, there is a need in the art for a method and system for improving operation and decreasing the recovery time of a modem that is ranging and registering following a network incident, such as a line break in a fiber ring of an HFC network.